WO2021140751A1

WO2021140751A1 - Structure

Info

Publication number: WO2021140751A1
Application number: PCT/JP2020/042952
Authority: WO
Inventors: 大未齊藤
Original assignee: 株式会社デンソー
Priority date: 2020-01-08
Filing date: 2020-11-18
Publication date: 2021-07-15
Also published as: JP7434901B2; US20220340797A1; CN114929473A; JP2021109336A

Abstract

A structure (1) has an aluminum substrate (111), and an adhesive layer (12) comprising an adhesive resin adhering to the surface of the aluminum substrate (111). The adhesive layer (12) comprises: a hard layer (121) contacting the adhesion interface (131) with the aluminum substrate (111); and a body layer (123) contacting the hard layer (121). The hard layer (121) is harder than the body layer (123).

Description

Structure

Cross-reference of related applications

This application is based on Japanese Application No. 2020-001210 filed on January 8, 2020, and the contents of the description are incorporated herein by reference.

This disclosure relates to structures.

Conventionally, a structure having an aluminum base material and an adhesive layer composed of an adhesive resin such as an epoxy resin adhered to the surface of the aluminum base material is widely known.

Further, as described in Patent Document 1, a structure in which a primer is applied between an aluminum base material and an adhesive layer composed of an adhesive resin is also known.

Japanese Unexamined Patent Publication No. 2000-239644

Conventionally widely known structures have a weak vicinity of the adhesive interface between the aluminum base material and the adhesive layer. Therefore, when the aluminum base material is in contact with the solvent for a long time or when a thermal shock is applied, peeling occurs at the adhesive interface between the aluminum base material and the adhesive layer.

An object of the present disclosure is to provide a structure capable of exhibiting high adhesive strength even when it is in contact with a solvent for a long time or when a thermal shock is applied.

One aspect of the present disclosure includes an aluminum base material and an adhesive layer made of an adhesive resin adhered to the surface of the aluminum base material.
The adhesive layer includes a hard layer in contact with the adhesive interface with the aluminum base material and a main body layer in contact with the hard layer.
The hard layer is harder than the main body layer,
It is in the structure.

According to the above structure, high adhesive strength can be exhibited even when it is in contact with a solvent for a long time or when a thermal shock is applied.

Note that the reference numerals in parentheses described in the claims indicate the correspondence with the specific means described in the embodiments described later, and do not limit the technical scope of the present disclosure.

The above objectives and other objectives, features and advantages of the present disclosure will be clarified by the following detailed description with reference to the accompanying drawings. The drawing is
FIG. 1 is a diagram schematically showing a structure according to the first embodiment. 2A and 2B are explanatory views of an estimation mechanism for improving the adhesive strength, FIG. 2A is a diagram schematically showing a state of the adhesive resin in the structure according to the first embodiment, and FIG. 2B is a diagram schematically showing a state of the adhesive resin according to the comparative embodiment. It is a figure which showed typically the state of the adhesive resin in a structure. FIG. 3 is a diagram schematically showing the relationship between the distance from the adhesive interface in the cross section of the adhesive layer and the adsorption force or elastic modulus. FIG. 4 is a diagram schematically showing the structure according to the second embodiment. FIG. 5 is a diagram showing an adsorption force image of a cross section of the adhesive layer of Sample 1 obtained by surface observation with a scanning probe microscope in Experimental Example 1. FIG. 6 is a diagram showing an adsorption force image of a cross section of the adhesive layer of Sample 1C obtained by surface observation with a scanning probe microscope in Experimental Example 1. FIG. 7 is a diagram showing an elastic modulus image of the cross section of the adhesive layer of Sample 1 obtained by surface observation with a scanning probe microscope in Experimental Example 1. FIG. 8 is a diagram showing an elastic modulus image of the cross section of the adhesive layer of Sample 1C obtained by surface observation with a scanning probe microscope in Experimental Example 1. FIG. 9 is a diagram showing the relationship between the distance from the adhesive interface and the adsorption force in the cross section of the adhesive layer of Sample 1 and Sample 1C obtained in Experimental Example 2. FIG. 10 is a diagram showing the relationship between the distance from the adhesive interface and the adsorption force in the cross section of the adhesive layer of Sample 2 and Sample 2C obtained in Experimental Example 2. FIG. 11 is a diagram showing the relationship between the distance from the adhesive interface and the elastic modulus in the cross section of the adhesive layer of Sample 1 and Sample 1C obtained in Experimental Example 2. FIG. 12 is a diagram showing the relationship between the distance from the adhesive interface and the elastic modulus in the cross section of the adhesive layer of Sample 2 and Sample 2C obtained in Experimental Example 2. FIG. 13 is a diagram showing the tensile shear strength of the structures of Sample 1 and Sample 1C obtained in Experimental Example 3 under each condition.

The structure of the present embodiment has an aluminum base material and an adhesive layer made of an adhesive resin adhered to the surface of the aluminum base material. The adhesive layer includes a hard layer in contact with the adhesive interface with the aluminum base material and a main body layer in contact with the hard layer. The hard layer is harder than the body layer.

The structure of the present embodiment can be broken mainly in the main body layer even when it is in contact with a solvent for a long time or when a thermal shock is applied. That is, in the structure of the present embodiment, the base metal fracture of the main body layer is mainly destroyed, not the interfacial fracture. This is because even if the adhesive layer is made of the same adhesive resin, the resin physical properties of the adhesive resin have not changed in the main body layer, while the hard layer is harder than the main body layer. It is considered that this is because the resin physical properties of the adhesive resin immobilized on the adhesive interface have changed and the strength near the adhesive interface has increased.
Therefore, according to the structure of the present embodiment, high adhesive strength can be exhibited even when the structure is in contact with a solvent for a long time or when a thermal shock is applied. This will be explained in detail below.

(Embodiment 1)
The structure of the first embodiment will be described with reference to FIGS. 1 and 2. As illustrated in FIG. 1, the structure 1 of the present embodiment has an aluminum base material 111 and an adhesive layer 12.

The aluminum referred to in the aluminum base material 111 includes not only pure aluminum but also an aluminum alloy. Specific examples of the aluminum base material 111 include base materials in various shapes of members made of aluminum or an aluminum alloy. Examples of aluminum alloys include 1000 series Al alloys, 2000 series Al alloys, 3000 series Al alloys, 4000 series Al alloys, 5000 series Al alloys, 6000 series Al alloys, 7000 series Al alloys, and aluminum die cast alloys such as ADC12. Can be mentioned.

Of the surface of the aluminum base material 111, at least the adhesive surface to which the adhesive layer 12 is adhered can be modified. Specifically, the adhesive surface can be removed in whole or in part from the oxide film layer (not shown). Further, a modified layer (not shown) made of silicate glass or the like can be provided on the surface of the adhesive surface from which all or part of the oxide film layer has been removed. According to this configuration, it becomes easy to form a covalent bond between the modified layer and the adhesive resin, and it becomes easy to exhibit high adhesive strength in combination with the effect of improving the strength near the adhesive interface 131. Examples of the silicate glass include aluminosilicate glass, which is a silicate glass in which an Al element is dissolved in a solid solution.

The adhesive layer 12 is composed of an adhesive resin adhered to the surface of the aluminum base material 111. Specifically, the adhesive layer 12 may be partially formed on the surface of the aluminum base material 111, or may be formed on the entire surface of the aluminum base material 111.

Examples of the adhesive resin include epoxy resin, polyurethane resin, melanin resin, urea resin, silicone resin, polyester resin and the like. Of these, epoxy resin and silicone resin are preferable as the adhesive resin. Since the epoxy resin and the silicone resin can form a covalent bond by a chemical reaction with an OH group that may exist on the surface of the aluminum base material 111, it is easy to improve the strength near the adhesive interface 131. For example, as described above, when the aluminum base material 111 has a modified layer composed of silicate glass on the surface, the epoxy resin is covalently bonded by a chemical reaction between the OH group and the epoxy group on the surface of the modified layer. Can occur. Further, the silicone resin can form a covalent bond with the OH group on the surface of the modified layer by a dehydration condensation reaction. The adhesive resin may contain one or more of various additives applied to general resin-based adhesives, if necessary.

The adhesive layer 12 includes a hard layer 121 and a main body layer 123. The hard layer 121 is in contact with the adhesive interface 131 with the aluminum base material 111. The main body layer 123 is in contact with the hard layer 121. Since both the hard layer 121 and the main body layer 123 are a part of the adhesive layer 12, they are basically integrally formed of the same type of adhesive resin constituting the adhesive layer 12. However, the state of the polymer constituting the adhesive resin is different between the hard layer 121 and the main body layer 123. Therefore, the hardness of the hard layer 121 and the main body layer 123 are different. Specifically, the hard layer 121 is harder than the main body layer 123.

The estimation mechanism that allows a structure having such a structure to exhibit high adhesive strength will be described. As illustrated in FIG. 2B, in the structure 1'in the comparative form, the adhesive layer 12'does not include the hard layer 121 and the main body layer 123, and the entire adhesive layer 12'is uniformly hard. It is said to be. In such a configuration, the crosslink density of the adhesive resin constituting the adhesive layer 12'is substantially the same in the thickness direction of the adhesive layer 12', and the strength near the adhesive interface 131 is not improved. Therefore, the conventional structure 1'is likely to be peeled off at the adhesive interface 131. On the other hand, in the structure 1 of the present embodiment, the adhesive layer 12 includes a hard layer 121 and a main body layer 123, and the hard layer 121 is harder than the main body layer 123. In such a configuration, the cross-linking density of the adhesive resin constituting the hard layer 121 is larger than the cross-linking density of the adhesive resin constituting the main body layer 123, and the strength in the vicinity of the adhesive interface 131 is improved by improving the cross-linking density. In FIG. 2, the intersections of the lattices shown in the adhesive layers 12 and 12'mean the cross-linking points. As a result, in the structure 1, the main body layer 123 having a relatively low strength is first destroyed (base metal fracture), and the interface fracture at the adhesive interface 131 is less likely to occur. Therefore, the structure 1 can exhibit high adhesive strength even when it is in contact with a solvent for a long time or when a thermal shock is applied.

The hard layer 121 can be configured to be bonded to the surface of the aluminum base material 111 by a covalent bond. According to this configuration, the solvent is less likely to penetrate into the adhesive interface 131 as compared with the configuration in which the surface of the aluminum base material 111 is bonded by an anchor effect or a hydrogen bond. Therefore, according to this configuration, the strength of the adhesive interface 131 is less likely to deteriorate, the effect of improving the strength of the adhesive interface 131 can be ensured, and the long-term adhesive reliability of the adhesive interface 131 is also improved. The hydrogen bond is broken by an attack by a solvent that has penetrated the adhesive interface 131, and the cut portion becomes a new reaction point and a chain reaction occurs. Therefore, the bond by hydrogen bond is more likely to deteriorate the adhesive interface 131 with respect to a solvent such as an organic solvent than the bond by covalent bond.

Here, since the hardness of the adhesive layer 12 is related to the cross-linking density of the adhesive resin as described above, the relationship between the distance from the adhesive interface 131 to the inside of the adhesive layer 12 and the cross-linking density is directly related. If the cross-linking density of the hard layer 121 is larger than the cross-linking density of the main body layer 123, it can be said that the hard layer 121 is harder than the main body layer 123. However, it is difficult to measure the crosslink density distribution of the adhesive resin in the adhesive layer 12. Therefore, as a result of repeated trial and error, the present inventor selects the adhesive force or elastic modulus of the adhesive resin as the resin physical properties, and the adsorption force of the hard layer 121 is larger than the adsorption force of the main body layer 123, or / and. It has been found that when the elastic modulus of the hard layer 121 is larger than the elastic modulus of the main body layer 123, the hard layer 121 can be said to be harder than the main body layer 123, and the above-mentioned effects can be obtained.

Specifically, as illustrated in FIG. 3, in the structure 1, the adsorption force of the hard layer 121 measured by using a scanning probe microscope with respect to the cross section of the adhesive layer 12 perpendicular to the adhesive interface 131 is the main body. The configuration can be larger than the adsorption force of the layer 123. Further, the structure 1 has a configuration in which the elastic modulus of the hard layer 121 measured by using a scanning probe microscope is larger than the elastic modulus of the main body layer 123 with respect to the cross section of the adhesive layer 12 perpendicular to the adhesive interface 131. be able to. According to these configurations, the above-mentioned action and effect can be ensured.

The adsorption force and elastic modulus can be measured as follows. A measurement sample having a cross section of the adhesive layer 12 perpendicular to the adhesive interface 131 is collected from the structure 1 to be measured. As the scanning probe microscope, a scanning probe microscope "SPM9500" manufactured by Shimadzu Corporation can be used. If the model is discontinued and cannot be obtained, a successor model can be used. A Si ₃ N ₄ AFM cantilever (Hitachi High-Tech Science "SN-AF01" (spring constant 0.08 N / m)) is used as the probe. The measurement mode of the scanning probe microscope is the contact mode, and the operation mode is the force curve mode. The frequency at the time of measurement is 1 Hz, and the contact voltage is 0.5 V. Using the scanning probe microscope, each position of the adhesive layer 12 is gradually separated from the adhesive interface 131 appearing in the cross section of the adhesive layer 12 in the measurement sample along the thickness direction of the adhesive layer 12. Measure the force curve in. That is, the distance from the adhesive interface 131 in the adhesive layer 12 to the inside of the adhesive layer 12 is gradually changed, and the force curve at each position of the cross section of the adhesive layer 12 is measured. Next, the elastic modulus and the attractive force at each position of the adhesive layer 12 cross section are obtained from the force curve at each position of the adhesive layer 12 cross section. According to the measurement by the scanning probe microscope, when the cantilever is brought close to the surface of the measurement sample and the cantilever comes into contact with the measurement sample, the cantilever is deflected on the repulsive force side. Then, when the cantilever begins to separate from the measurement sample, the deflection of the cantilever decreases, but the suction force generated between the surface of the measurement sample and the cantilever causes the deflection on the attractive force side, contrary to the above. After that, the cantilever completely separates from the surface of the measurement sample. The elastic modulus can be obtained from the amount of deflection of the force curve portion corresponding to the portion where the cantilever is deflected to the repulsive force side. The suction force can be obtained from the amount of deflection of the force curve portion corresponding to the portion that separates from the measurement sample after the cantilever bends to the attractive force side. As a result, as illustrated in FIG. 3, the relationship between the distance from the adhesive interface 131 in the cross section of the adhesive layer 12 and the adsorption force, and the relationship between the distance from the adhesive interface 131 in the cross section of the adhesive layer 12 and the elastic modulus. The figure is obtained. In the above relationship diagram, the region where the adsorption force or elastic modulus hardly changes depending on the distance from the adhesive interface 131 corresponds to the main body layer 123, and the adsorption force or elastic modulus is larger than that of the main body layer 123, from the adhesive interface 131. The region where the adsorption force or the elastic modulus changes depending on the distance corresponds to the hard layer 121. As described above, the hard layer 121 in the adhesive layer 12 has a region in which the adhesive force or elastic modulus of the adhesive resin immobilized on the adhesive interface 131 changes as compared with the adhesive force or elastic modulus of the adhesive resin in the main body layer 123. Can be grasped as.

When the structure 1 has a structure in which the suction force of the hard layer 121 is larger than the suction force of the main body layer 123, the suction force of the hard layer 121 can be reduced as the distance from the adhesive interface 131 increases. According to this configuration, it is possible to ensure the strength improvement of the adhesive interface 131, so that the above-mentioned action and effect can be ensured. Further, by changing the state of the adhesive resin little by little, the number of parts where stress is concentrated is reduced, and there is an advantage that the force is less likely to be applied near the adhesive interface 131. The adsorption force of the hard layer 121 may gradually decrease as the distance from the adhesive interface 131 increases, or may decrease stepwise (stepwise) as the distance from the adhesive interface 131 increases.

Similarly, in the structure 1, when the elastic modulus of the hard layer 121 is larger than the elastic modulus of the main body layer 123, the elastic modulus of the hard layer 121 is set to decrease as the distance from the bonding interface 131 increases. Can be done. According to this configuration, it is possible to ensure the strength improvement of the adhesive interface 131, so that the above-mentioned action and effect can be ensured. In addition, since the displacement due to stress changes stepwise, there is an advantage that it becomes easy to prevent sudden stress concentration due to the displacement difference. The elastic modulus of the hard layer 121 may gradually decrease as the distance from the adhesive interface 131 increases, or may decrease stepwise (stepwise) as the distance from the adhesive interface 131 increases.

In the structure 1, the thickness of the hard layer 121 can be 0.5 μm or more. According to this configuration, the adsorption force and elastic modulus are higher in the vicinity of the adhesive interface 131, and the density of the adhesive resin is higher, so that the adhesive resin in the vicinity of the adhesive interface 131 is prevented from being weakened by the permeated solvent or permeated gas. There are advantages such as easy operation. The thickness of the hard layer 121 can be preferably 1 μm or more, more preferably 2 μm or more, still more preferably 5 μm or more, from the viewpoint of facilitating solvent permeation and gas permeation of the adhesive resin. Further, in this case, when the entire adhesive resin is hardened, the thickness of the hard layer 121 may increase the density of the adhesive resin, reduce the flexibility of the adhesive resin, and may be weak against thermal shock or the like. From the viewpoint of facilitating prevention, the thickness can be preferably 2 mm or less. The thickness of the hard layer 121 is shown in the relationship diagram between the distance from the adhesive interface 131 in the cross section of the adhesive layer 12 and the adsorption force, and the relationship diagram between the distance from the adhesive interface 131 in the cross section of the adhesive layer 12 and the elastic coefficient. Therefore, it can be obtained as the distance from the adhesive interface 131 to the interface between the hard layer 121 and the main body layer 123.

The adhesive layer 12 in the structure 1 of the present embodiment can be used, for example, as a resin coat on the surface of the aluminum base material 111, a sealing material formed on the surface of the aluminum base material 111, or the like.

(Embodiment 2)
The structure 1 of the second embodiment will be described with reference to FIG. In addition, among the codes used in the second and subsequent embodiments, the same codes as those used in the above-described embodiments represent the same components and the like as those in the above-mentioned embodiments, unless otherwise specified.

As illustrated in FIG. 4, the structure 1 of the present embodiment has an aluminum base material 111 and an adhesive layer 12 similar to the structure 1 of the first embodiment. The structure 1 of the present embodiment further has an aluminum base material 112. Specifically, the structure 1 of the present embodiment is arranged between the aluminum base material 111, the aluminum base material 112, and the

aluminum base materials

111 and 112, and the surface of the aluminum base material 111 and the aluminum base material 112. It has an adhesive layer 12 made of an adhesive resin adhered to the surface of the above. That is, the structure 1 of the present embodiment is a bonded structure in which the aluminum base material 111 and the aluminum base material 112 are joined via the adhesive layer 12.

As illustrated in FIG. 4, more specifically, the adhesive layer 12 has a hard layer 121 in contact with the adhesive interface 131 with the aluminum base material 111 and a hard layer 122 in contact with the adhesive interface 132 with the aluminum base material 112. And a main body layer 123 in contact with the hard layer 121 and the hard layer 122. The hard layer 121 is harder than the main body layer 123, and the hard layer 122 is harder than the main body layer 123. The aluminum base material 112, the adhesive interface 132, and the hard layer 122 can be similarly configured with reference to the description of the aluminum base material 111, the adhesive interface 131, and the hard layer 121 described in the first embodiment. The aluminum base material 112 may be made of the same aluminum alloy or the like as the aluminum base material 111, or may be made of a different aluminum alloy or the like.

In the present embodiment, the above-mentioned aluminum base material 111 is the first aluminum base material, the aluminum base material 112 is the second aluminum base material, the hard layer 121 is the first hard layer, the hard layer 122 is the second hard layer, and adhesion. The interface 131 can be said to be the first adhesive interface, and the adhesive interface 132 can be said to be the second adhesive interface.

According to the structure 1 of the present embodiment, a bonded structure capable of exhibiting high adhesive strength can be obtained even when it is in contact with a solvent for a long time or when a thermal shock is applied.

In the structure 1, the thicknesses of the

hard layers

121 and 122 can be 1 μm or more. According to this configuration, there are advantages such as an improvement in elastic modulus, an increase in strength of the

adhesive interfaces

131 and 132, and difficulty in cutting at the

adhesive interfaces

131 and 132 and their vicinity. The thickness of the

hard layers

121 and 122 can be preferably 2 μm or more, more preferably 3 μm or more, still more preferably 5 μm or more, from the viewpoint of improving the strength of the

adhesive interfaces

131 and 132. Further, in this case, the thickness of the

hard layers

121 and 122 can be preferably 2 mm or less from the viewpoint of preventing the elastic modulus from becoming too high and making it difficult for the internal stress to escape.

The structure 1 of the present embodiment can be used for joining an aluminum member and an aluminum member. More specifically, the structure 1 of the present embodiment includes joining of aluminum pipes and piping members (for example, joint members, fixing members, etc.), joining of pipes, and joining of heat exchanger members. It can be applied in various ways to join heat exchangers and parts around the heat exchangers, such as joining heat exchangers and pipes. Other configurations and effects are the same as in the first embodiment.

(Experimental example)
<Experimental example 1>
-Preparation of sample 1 and sample 1C-
After alkaline cleaning of an aluminum base material with an oxide film layer having a shape of length l = 40 mm, width w = 10 mm, and thickness t = 1 mm, this is pH 12.4, liquid temperature 50 ° C., sodium silicate concentration 0. It was immersed in a .4 mol / L sodium silicate aqueous solution for 1 minute, and then washed with pure water. As a result, the surface of the aluminum base material was modified. The modified layer on the surface of the aluminum base material is a thin film layer made of silicate glass in which Al element is solid-solved, which is formed from an oxide film _{layer made of Al 2} O _3.

Next, the two aluminum base materials prepared as described above were arranged so as to overlap over a range of 10 mm in length with a gap formed between the base material surfaces at each end. The gap interval was set to 200 μm. Next, an adhesive resin material was applied to the end of the gap. As the adhesive resin material, an epoxy resin material composed of 2,2-bis (4-hydroxyphenyl) propandiglycidyl ether (BPADGE) as a main agent and dicyandiamide (DYCI) as a curing agent was used. Then, by heating to 80 ° C., the adhesive resin material was reduced in viscosity and fluidly moved to fill the gap. As a result, a laminate having a laminated structure in which the aluminum base material / adhesive resin material / aluminum base material was laminated in this order was obtained.

Next, the obtained laminate was heated and held at 135 ° C. for 10 minutes, then the heating temperature was further raised and held at 155 ° C. for 20 minutes to cure the adhesive resin material, and then naturally cooled. As a result, the structure of the sample 1 having the aluminum base material and the adhesive layer composed of the epoxy resin adhered to the surface of the aluminum base material (specifically, the aluminum base material / adhesive layer / aluminum base material in this order). A structure having a laminated structure laminated in 1) was obtained. In the structure of Sample 1, the adhesive resin of the hard layer is covalently bonded to the surface of the modified aluminum base material.

Next, in the preparation of the structure of the sample 1, the aluminum base material and the epoxy resin adhered to the surface of the aluminum base material were formed in the same manner except that the aluminum base material was not immersed in the sodium silicate aqueous solution. A structure of sample 1C having an adhesive layer to be formed (specifically, a structure having a laminated structure in which an aluminum base material / an adhesive layer / an aluminum base material is laminated in this order) was obtained.

-Preparation of sample 2 and sample 2C-
In the production of the structure of Sample 1, an epoxy-modified silicone resin material ("DOWNSIL SE1714" manufactured by Dow Toray Co., Ltd.) was used as the adhesive resin material, and the bases of each end of the two aluminum base materials. A point obtained by applying the above-mentioned silicone resin material on the material surface so as to overlap over a length of 10 mm and laminating the material so that the distance between the base material surfaces at each end is 200 μm to form a laminate. The laminated body was heated and held at 140 ° C. for 5 minutes, then further raised in heating temperature, held at 170 ° C. for 5 minutes, and then naturally cooled in the same manner as the aluminum base material and the aluminum base material. A structure of Sample 2 having an adhesive layer composed of the above-mentioned silicone resin adhered to the surface of the sample 2 was obtained. In the structure of Sample 2, the adhesive resin of the hard layer was a modified aluminum base material. It is bonded to the surface by a covalent bond.

Next, in the preparation of the structure of the sample 2, the aluminum base material and the silicone resin adhered to the surface of the aluminum base material were obtained in the same manner except that the aluminum base material was not immersed in the sodium silicate aqueous solution. A structure of sample 2C having an adhesive layer to be formed was obtained.

-Measurement of adsorption force image by scanning probe microscope-
A measurement sample having a cross section of an adhesive layer perpendicular to the adhesive interface was taken from the structures of Sample 1 and Sample 1C. For the measurement sample, each structure was cut with a wire saw, and then a cross section was prepared with FIB. The same applies hereinafter. Next, the cross section of each adhesive layer was surface-observed with a scanning probe microscope, and the adsorption force image of each adhesive layer was measured. The adsorption force image was obtained by performing the measurement under the above-mentioned measurement conditions on the entire cross section to obtain and map the adsorption force for each point of each part. An image of the adsorption force of the cross section of the adhesive layer of Sample 1 is shown in FIG. An image of the adsorption force of the cross section of the adhesive layer of Sample 1C is shown in FIG.

As shown in FIG. 6, the adhesive layer of the structure of sample 1C had a substantially constant adsorption force over the entire adhesive layer. From this, it can be seen that in the structure of Sample 1C, the crosslink density of the epoxy resin constituting the adhesive layer does not change in the thickness direction, and the entire adhesive layer has a uniform hardness. That is, it can be seen that the adhesive layer of the structure of sample 1C does not include the hard layer and the main body layer. On the other hand, as shown in FIG. 5, in the adhesive layer of the structure of sample 1, the adsorption force of a certain region from the adhesive interface between the aluminum base material and the adhesive layer to the adhesive layer side is within the constant region. It was larger than the adsorption force of the adhesive layer on the other side. From this, in the structure of Sample 1, the crosslink density of the epoxy resin constituting the adhesive layer changes in the thickness direction, and the crosslink density of a certain region from the adhesive interface to the adhesive layer side is within the above constant region. It can be said that it is higher than the crosslink density of the adhesive layer on the other side. That is, it can be seen that the adhesive layer of the structure of the sample 1 includes an internal main body layer and a hard layer harder than the main body layer. As for the structures of Sample 2 and Sample 2C, the same results as those of Sample 1 and Sample 1C were obtained.

-Measurement of elastic modulus image with scanning probe microscope-
A measurement sample having a cross section of an adhesive layer perpendicular to the adhesive interface was taken from the structures of Sample 1 and Sample 1C. Next, the cross section of each adhesive layer was surface-observed with a scanning probe microscope, and the elastic modulus image of each adhesive layer was measured. The elastic modulus image was obtained by performing the measurement under the above-mentioned measurement conditions on the entire cross section to obtain the elastic modulus for each point of each part and mapping. An elastic modulus image of the cross section of the adhesive layer of Sample 1 is shown in FIG. An elastic modulus image of the cross section of the adhesive layer of Sample 1C is shown in FIG.

As shown in FIG. 8, the elastic modulus of the adhesive layer of the structure of Sample 1C was substantially constant over the entire adhesive layer. From this, it can be seen that in the structure of Sample 1C, the crosslink density of the epoxy resin constituting the adhesive layer does not change in the thickness direction, and the entire adhesive layer has a uniform hardness. That is, it can be seen that the adhesive layer of the structure of sample 1C does not include the hard layer and the main body layer. On the other hand, as shown in FIG. 7, in the adhesive layer of the structure of the sample 1, the elastic modulus of a certain region from the adhesive interface between the aluminum base material and the adhesive layer to the adhesive layer side is within the constant region. It was larger than the elastic modulus of the adhesive layer on the other side. From this, in the structure of Sample 1, the crosslink density of the epoxy resin constituting the adhesive layer changes in the thickness direction, and the crosslink density of a certain region from the adhesive interface to the adhesive layer side is within the above constant region. It can be said that it is higher than the crosslink density of the adhesive layer on the other side. That is, it can be seen that the adhesive layer of the structure of the sample 1 includes an internal main body layer and a hard layer harder than the main body layer. As for the structures of Sample 2 and Sample 2C, the same results as those of Sample 1 and Sample 1C were obtained.

<Experimental example 2>
-Relationship between the distance from the adhesive interface and the adsorption force or elastic modulus in the cross section of the adhesive layer-
A measurement sample having a cross section of an adhesive layer perpendicular to the adhesive interface was taken from the structures of Sample 1 and Sample 1C. Next, the cross section of each adhesive layer is surface-observed with a scanning probe microscope under the above-mentioned measurement conditions, and the relationship between the distance from the adhesive interface in the cross section of the adhesive layer and the adsorption force, and the adhesive interface in the cross section of the adhesive layer. The relationship between the distance and the elasticity was measured. FIG. 9 shows the relationship between the distance from the adhesive interface and the adsorption force in the cross section of the adhesive layer of Sample 1 and Sample 1C. FIG. 10 shows the relationship between the distance from the adhesive interface and the adsorption force in the cross section of the adhesive layer of Sample 2 and Sample 2C. FIG. 11 shows the relationship between the distance from the adhesive interface and the elastic modulus in the cross section of the adhesive layer of Sample 1 and Sample 1C. FIG. 12 shows the relationship between the distance from the adhesive interface and the elastic modulus in the cross section of the adhesive layer of Sample 2 and Sample 2C.

As shown in FIGS. 9 and 10, FIGS. 11 and 12, it can be seen that the structures of Sample 1C and Sample 2C have constant adsorption force and elastic modulus regardless of the distance from the adhesive interface. From this, it can be seen that in the structures of Sample 1C and Sample 2C, the crosslink density of the adhesive resin constituting the adhesive layer does not change in the thickness direction, and the entire adhesive layer has a uniform hardness. On the other hand, as shown in FIGS. 9 and 10, FIG. 11 and FIG. 12, the adhesive layer of the structures of Sample 1 and Sample 2 is constant from the adhesive interface between the aluminum base material and the adhesive layer to the adhesive layer side. The adsorption force and elastic modulus up to a distance were larger than the adsorption force and elastic modulus of the adhesive layer at a distance exceeding the above-mentioned constant distance. From this, in the structures of Sample 1 and Sample 2, the cross-linking density of the adhesive resin constituting the adhesive layer changes in the thickness direction, and the cross-linking density of a certain distance from the adhesive interface to the adhesive layer side is the above-mentioned constant distance. It can be said that it is larger than the crosslink density of the inner adhesive layer. That is, it can be seen that the adhesive layer of the sample 1 and sample 2 structures includes an internal main body layer and a hard layer harder than the main body layer. Further, the hard layers in the structures of Sample 1 and Sample 2 both became smaller as the distance from the adhesive interface increased.

<Experimental example 3>
The structure of sample 1 and sample 1C in the initial state, the structure of sample 1 and sample 1C immersed in tetrahydrofuran (THF) for 18 hours, the heat cycle of heating to 50 ° C. and then cooling to -196 ° C. was repeated 10 times. The tensile shear strength of each of the structures of Sample 1 and Sample 1C was measured. A universal test device (manufactured by Shimadzu Corporation, "Autograph") was used for the measurement. The measurement conditions were a tensile speed of 5 mm / min, a grip width of 10 mm, and the number of measurements = 6. The result is shown in FIG.

As shown in FIG. 13, the structure of sample 1 had a higher initial tensile shear strength than the structure of sample 1C. This is because the structure of Sample 1C does not have a hard layer as the adhesive layer, and the adhesive resin is adhered to the surface of the aluminum base material by an anchor effect, hydrogen bonds, or the like. On the other hand, in the structure of Sample 1, in addition to the strength near the adhesive interface being improved by the hard layer, the effect that the adhesive resin of the hard layer is covalently bonded to the surface of the aluminum base material is also combined. It is probable that the initial tensile shear strength increased.

Further, as shown in FIG. 13, the structure of sample 1 has less decrease in tensile shear strength and higher tensile strength than the structure of sample 1C in both cases after immersion in THF and after loading with a thermodynamic cycle. Shear strength could be maintained. The fracture form of the sample 1 was mainly the fracture of the base material of the main body layer, but the structure of the sample 1C was mainly the interface peeling. Further, with respect to the structures of Sample 2 and Sample 2C, the same results as those of the structures of Sample 1 and Sample 1C were obtained.

The present disclosure is not limited to each of the above embodiments and experimental examples, and various changes can be made without departing from the gist thereof. In addition, each configuration shown in each embodiment and each experimental example can be arbitrarily combined. That is, although the present disclosure has been described in accordance with the embodiments, it is understood that the present disclosure is not limited to the embodiments, structures, and the like. The present disclosure also includes various modifications and modifications within an equal range. In addition, various combinations and forms, as well as other combinations and forms that include only one element, more, or less, are also within the scope of the present disclosure.

Claims

It has an aluminum base material (111, 112) and an adhesive layer (12) made of an adhesive resin adhered to the surface of the aluminum base material.
The adhesive layer includes a hard layer (121, 122) in contact with the adhesive interface (131, 132) with the aluminum base material, and a main body layer (123) in contact with the hard layer.
The hard layer is harder than the main body layer,
Structure (1).
With respect to the cross section of the adhesive layer perpendicular to the adhesive interface, the adsorption force of the hard layer measured using a scanning probe microscope is larger than the adsorption force of the main body layer.
The structure according to claim 1.
The adsorption force of the hard layer decreases as the distance from the adhesive interface increases.
The structure according to claim 2.
With respect to the cross section of the adhesive layer perpendicular to the adhesive interface, the elastic modulus of the hard layer measured using a scanning probe microscope is larger than the elastic modulus of the main body layer.
The structure according to any one of claims 1 to 3.
The elastic modulus of the hard layer decreases as the distance from the adhesive interface increases.
The structure according to claim 4.
The adhesive resin is an epoxy resin or a silicone resin.
The structure according to any one of claims 1 to 5.
The thickness of the hard layer is 0.5 μm or more.
The structure according to any one of claims 1 to 6.
The thickness of the hard layer is 1 μm or more.
The structure according to any one of claims 1 to 6.